Skip to main content

Full text of "An Australian Leptanilla."

See other formats

[Reprinted from PSYCHE. Vol. XXXIX. No. 3 (1 932)] 




By William Morton Wheeler 
Harvard University 

The very interesting Formicid subfamily Leptanillinae 
comprises only two genera of minute, yellow, blind and 
hypogseic ants, namely, Leptanilla, established by Emery 
as long ago as 1870 and Phaulomyrma, established by G. C. 
and E. W. Wheeler in 1930 on a male specimen from 
Java. This genus probably also includes Santschi's L. tanit 
from Tunis. Of the eleven described species of Leptanilla, 
four are known only from males; of the remaining seven, 
five are known only from workers and only two from both 
workers and females. The geographical distribution of the 
various species is peculiar. Six of them, namely, L. theryi 
Forel, vaucheri Emery, exigua Santschi, minuscula Sants- 
chi, nana Santschi and tenuis Santschi, were taken in 
North Africa (Algiers, Tunis, Morocco), two, doderoi Em- 
ery and revelierei Emery, in Corsica and Sardinia (though 
the subspecies chohawti Emery of revelierei occurs in Mo- 
rocco), two, havilandi Forel and butteli Forel, in the Malay 
Peninsula and one, santschii G. C. and E. W. Wheeler, in 

During November, 1931, while I was with the Harvard 
Zoological Expedition in Australia, Mr. D. C. Swan of the 
Waite Institute at Glen Osmond, S. A., generously gave me 
some minute ants which he discovered in Western Austra- 

- S'l- 

54 Psyche [September 

lia. The collection comprises two dozen workers, a female 
and a number of full-grown larvae, which prove to belong 
to an undescribed species of Leptanilla. They therefore 
considerably extend the known geographical range of the 
genus. Owing to the fact that the Leptanillinse are true 
members of Silvestri's "microgenton" and that their work- 
ers and females are very rarely seen, because they come to 
the surface of the soil only under unusual conditions, such 
as excessive rainfall, it is too early to regard the various 
species at present known as covering the entire range of 
the genus. We should expect careful collecting with the 
Berlese funnel to bring additional forms to light in South 
Africa, Madagascar, Asia Minor and India, or even, per- 
haps, in the warmer parts of the New World. 

Leptanilla swani sp. nov. 

Worker. (Fig. 1, a-d.) Length 1.3-1.5 mm. Pale yellowy 
legs scarcely paler than the body ; teeth and borders of the 
mandibles reddish. 

Head flattened above, oblong, fully li/^ times as long as 
broad, as broad in front as behind, with subparallel sides, 
rounded posterior corners and feebly concave posterior 
border. Mandibles narrow, with very oblique 4-toothed 
apical borders, the terminal tooth curved and acute, the 
second minute, the two remaining teeth stout and rather 
blunt, the most basal directed at right angles to the apical 
border or even slightly backward. Clypeus without distinct 
posterior suture, its anterior border slightly but distinctly 
produced in the middle as a broadly rounded lobe, excised 
at the sides. Antennae moderately stout; scapes reaching 
nearly to the middle of the head; basal funicular joint 
nearly li/^ times as long as broad, ovoidal, with constricted 
base; joints 2-6 distinctly broader than long; the second 
basally constricted, the seventh distinctly longer, 8-10 as 
broad as long, the terminal joint as long as the two preced- 
ing joints together. Thorax much narrower than the head 
including the mandibles, flattened dorsally and not deeply 
notched in profile at the promesonotal suture; pronotum 
subovoidal, somewhat broader than the mesepinotum, which 
is longer than the pronotum, with feebly rounded, sub- 
parallel sides. Petiole much narrower than the epinotum. 


An Australian Leptanilla 


nearly II/2 times as long as broad, gradually narrowed an- 
teriorly, posteriorly with rounded-subparallel sides. Post- 
petiole rounded-trapezoidal, nearly as long as broad, some- 
what broader than the petiole and somewhat wider behind 
than in front, its ventral surface convex and projecting. 
Gaster narrow, elongate-elliptical, anterior border of first 
segment slightly concave. Sting large, retracted. Legs mod- 

FlG. 1. Leptanilla sivani sp. nov. a, worker; b, clypens and mandible 

of same; c, antenna; d, fore tibia and tarsus; e, female; 

/, clypeus and mandible of same. 

erately stout, tips of fore metatarsi produced and digiti- 
form, but not so narrowly as in L. narm Santschi. 

Shining, with very fine and indistinct piligerous punc- 
tures. Pilosity white, very short, abundant both on the 
body and antennse, slightly longer and coarser on the gaster, 
less conspicuous and more dilute and appressed on the legs. 

Female. (Fig. 1, e and f.) Length 2 mm. 

Color, sculpture and pilosity as in the worker, but the 
hairs on the gaster very long, though fine, as in the female 
of L. theryi Forel. 

56 Psyche [September 

Apterous and resembling the worker in form but differing 
in the following characters : Head more sharply oblong, 
with straight and more clearly parallel sides. Mandibles 
falcate, narrow and tapering at the tips, without distinct 
basal and apical borders, terminating in two small, indis- 
tinct, closely approximated teeth. Clypeus broader and less 
produced than in the worker. Thorax decidedly longer than 
the head plus the mandibles, very low and flat above, the 
pronotum posteriorly nearly as broad as the head, longer 
than broad, with feebly rounded, anteriorly converging 
sides, mesepinotum broader than the head, subtrapezoidal, 
broadest near the anterior end, roundly subtruncate behind. 
Promesonotal suture pronounced, straight and transverse 
in the middle. Petiole regularly oblong, about I14 longer 
than broad, as broad in front as behind. Gaster much 
larger than in the worker, the postpetiole, which forms its 
first segment, nearly twice as broad as long, subtrape- 
zoidal, with straight anterior border. Genitalia similar to 
those of L. revelierei Emery, but the pygidium with entire, 
broadly and semicircularly rounded posterior border, not 
notched in the middle. Hypopygium large, narrowed and 
bluntly bidentate posteriorly. Legs longer and stouter than 
in the worker. 

Described from 24 workers and a single female taken 
Oct. 10, 1931 by Mr. D. C. Swan under a large stone at 
Goyamin Pool, Chittering, Western Australia. 

L. swani seems to be most closely related to L. revelierei, 
but the female of the latter has a much shorter petiole. In 
the long pilosity of the gaster the female of the new form 
resembles theryi, but in this species the petiole is very 
different, being distinctly cordate anteriorly instead of 

Dr. G. C. Wheeler, to whom I sent the larvae of L. swani 
for study, writes me that he found them "extremely inter- 
esting because of their close resemblance to the larvae of 
revelieri subsp. sardoa. They even have the 'tympanum' 
which is difficult to detect unless the specimens are stained. 
This species differs from sardoa in the following charac- 
teristics: (1) The head is sharply constricted just in front 
of the middle so that in dorsal view it is flask-shaped or key- 
hole shaped ; the posterior half is circular, the middle half 

1932] An Aiistralian Leptanilla 57 

is about half as wide and has subparallel sides. (2)^The 
prothorax is sparsely spinulose while the curious structure 
oji its ventral surface has its base densely and coarsely 
spinulose. (3) The two extremely long hairs at the poste- 
rior end are lacking in all specimens." 

Emery, as is well known, regarded the Leptanillinse as 
constituting a special tribe of the Dorylinse, but Dr. G. C. 
Wheeler and I have raised the group to subfamily rank. 
Unquestionably, Emery, in his paper of 1904, based his 
opinion very largely on the singular characters of the fe- 
male, which he regarded as a true dichthadiigyne and com- 
pared with the female of Aenictus. Strangely enough, Em- 
ery seems not to have noticed the peculiar falcate shape of 
the female mandibles, so unlike those of the worker, a char- 
acter which, taken together with the absence of wings and 
the single segment of the pedicel, makes the resemblance to 
the females of the Dorylinse even greater than he supposed. 
But the males of the Leptanillinse and the larvse, as described 
and figured by G. C. Wheeler, are so very unlike those of the 
Dorylinse that we are bound to regard the striking similari- 
ties of the females as due to convergence. Emery's original 
interpretation of the thoracic segmentation of the female 
Leptanilla was incorrect, because he regarded the portion 
of the thorax anterior to the pronounced transverse dorsal 
suture as the mesonotum, the portion posterior to the suture 
as the combined metanotum and epinotum. In a foot-note 
to his section on the Leptanillinse in the "Genera Insecto- 
rum" (1910), he recognized his error and adopted the in- 
terpretation which I have also reached, namely, that the 
presutural portion is the pronotum, the postsutural the com- 
bined meso- and epinotum. 

The occurrence of indigenous species of Leptanilla on is- 
lands like Corsica, Sardinia, Java and Australia is signifi- 
cant. Since the females are apterous and obviously too 
small and delicate to endure distant transportation in flot- 
sam and jetsom, we must suppose that they have occupied 
their present habitats since the islands mentioned were 
connected with the mainland. The Leptanillinse, therefore, 
must be very ancient, like many other components of the 
microgenton (Kcenenia, Pauropus, Scolopendrella, Cam- 
podea, lapyx, etc.) L. swani is particularly interesting in 

58 Psyche [September 

this connection, because the extreme southwestern corner of 
Australia, in which it was taken, is known to possess the 
oldest and least disturbed fauna of any portion of the con- 


Emerif, C. Studi Mirmecologici. Bull. Soc. Ent. Ital. 2, 1870, pp. 193- 

201, 1 pi. 
Emery, C. Le affinita del genera DeptanlUa e i limiti delle Dorylinse. 

Archiv. Zool. Ital. 2, 1904, pp. 107-116, 9 figs. 
Emery, C. Pormicidae, subfam. Dorylinse, in Wytsman's Genera In- 

sectorum, 1910, pp. 32-33. 
Wheeler, a. 0. The Larva of Leptanilla. Psyche 35, 1928, pp. 85-91, 

1 fig. 
Wheeler, G. G. and E. W. Two New Ants from Java. Psyche 37, 1930, 

pp. 193-201, 2 figs.